Apparently if I understood the trick correctly, they have a fast spinning oscillator, and when they disable the oscillator mode it continues to spin but the last value is kept, so this can be used to generate a fine tuned volume control just by waiting a certain amount of time.

That's indeed hard to reproduce on the Oric, that would be like if the envelope mode had more than 16 volume levels and when switching from envelope to normal mode, it would keep the current volume.

I'm currently investigating the feasibility on the Oric of some programming method discussed on the MSX forums (MSX has the same soundchip as the oric).

The two main things they are doing is:
- Take into consideration the it takes to set a value in one of the particular registers of the YM to reduce spikes that happens when the three sets of registers are not finished being updated.
- Doing an incremental (delta) encoding of the samples to change the registers in a way that only changes as few as possible values to represent the new set of values that makes a sample

The two objectives I try to get some (all would be awesome) of these:
- Faster than 8 bit replay routines (more free cpu time)
- Same or better quality compared to 8 bit replay routines
- Less storage space for the samples